fix(ssh): verify the host key netOrk expects, report the one seen (NetOrk/netork#1167)

The driver accepted any SSH host key. It now verifies through
napalm-device-types' HostKeyCheck (>= 4.19.0): with a known key in
optional_args["ssh_host_keys"] any other key is refused before login, and
every key seen is reported to optional_args["ssh_host_key_observer"].
Without either argument it connects as before (first use).

napalm_proxmox/vm_provision_mixin.py

@@ -143,31 +143,7 @@ class ProxmoxVMProvisionMixin:
         disk import — where a non-zero exit or a caller-specific timeout must
         surface as a hard failure rather than an empty string.
         """
-        import paramiko
-
-        if self._ssh_client is None:
-            ssh_user = self._ssh_username or self.username
-            ssh_pass = self._ssh_password or self.password
-            ssh_pkey = None
-            if self._ssh_key and not ssh_pass:
-                from io import StringIO as _StringIO
-
-                ssh_pkey = paramiko.RSAKey.from_private_key(_StringIO(self._ssh_key))
-            self._ssh_client = paramiko.SSHClient()
-            self._ssh_client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
-            connect_kwargs: Dict[str, Any] = {
-                "hostname": self.hostname,
-                "port": 22,
-                "username": ssh_user,
-                "timeout": self.timeout,
-            }
-            if ssh_pkey:
-                connect_kwargs["pkey"] = ssh_pkey
-            else:
-                connect_kwargs["password"] = ssh_pass
-            self._ssh_client.connect(**connect_kwargs)
-
-        _, stdout, stderr = self._ssh_client.exec_command(command, timeout=timeout)
+        _, stdout, stderr = self._node_ssh().exec_command(command, timeout=timeout)
         exit_status = stdout.channel.recv_exit_status()
         out = stdout.read().decode().strip()
         err = stderr.read().decode().strip()